Refactor sample pack update logic and improve tag handling

Commit notes

- Simplified the UpdateSamplePack handler by removing unnecessary request body parsing and directly handling multipart form data. - Enhanced tag management by allowing empty arrays to clear tags and ensuring consistent updates for description, public status, price, and license text. - Updated frontend PackManager component to handle tags as an array, improving user experience and data consistency. - Added debug logging for pack updates and fetching, which can be removed in production.